Transformer bobbin



June 15, 1965 JONES 3,189,857

TRANSFORMER BOBBIN Filed D60. 31, 1962 2 IIIIIHNIH How T'd T. d was 138 fik s drew-neg lnven tow':

United States Patent 3,189,357 RANSFURMER BQBBIN Howard T. .lones, Hendcrsonviile, NC, assignor to General Electric Qompany, a corporation of New York Fifigd Dec. 31, 1962, Ser. No. 243,656 2 Claims. (6i. 336I.3)

This invention relates to transformers and more particularly to a winding bobbin for transformer coils.

It is an object of this invention to provide an improved insulating bobbin for a transformer which permits a pre cision wound coil to be readily made, handled and assembled with the core.

It is common practice in the transformer art to precision Wind transformer coils. It is also well recognized that the coils when placed on the transformer core must be insulated therefrom. It is an object of this invention to provide a winding bobbin which acts as a form for precision winding a coil and is utilized as the insulation in the completed transformer. More specifically, it is an object of this invention to provide a winding bobbin made of a plastic insulating material which includes means for controlling the spacing of the coil windings on the bobbin.

As is well recognized, the wire used in winding transformer coils is normally of the type which has an insulating enamel thereon. In winding coils which are generally rectangular in shape so as to more nearly correspond to the shape of the core, care must be taken to prevent cracking of the insulating enamel. It is therefore an object of this invention to provide a winding bobbin on which the wire is wound which is of a rectangular shape with rounded corners so as to increase the bending radius of the wire and eliminate the enamel cracking problem.

In the assembling of transformers, workers have a tendency to use the outwardly extending ends of a wound coil as a handle with which to carry the coil. This is a distinct disadvantage, since during such handling, the windings are misplaced each from the other and the advantages of precision winding are sometimes lost. It is a further object of this invention to provide a winding bobbin for a transformer coil which secures the ends of the windings so that they cannot be used as a handle with which to carry the wound coil.

In accordance with the above mentioned objects, there is provided a winding bobbin for a transformer which comprises a tube having integral end flanges for constraining the coil on the tube. The tube is provided with rounded corners on its exterior so as to increase the bending radius at the corners and prevent breaking of the insulating enamel on the coil wire. To control the spacing of the windings on the bobbin there are provided pyramidal ribs on the rounded corners which are spaced apart a distance equal to, or slightly greater than, the diameter of the wire to be used in winding the coil. A Winding offsetting wedge is provided on one surface of the tube to lead the second turn of wire along side the edge of the first completed turn. In accordance with further objects of the invention there are provided means on said bobbin for securing the end of the coil windings to said bobbin so that the windings will not be misplaced during handling and assembling of the transformer.

Other objects and advantages will be apparent from the complete description and the drawings wherein;

FIG. 1 is a perspective view of the bobbin with a coil wound thereon;

FIG. 2 is an end view thereof;

FIG. 3 is a cross sectional view thereof without the complete coil;

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FIG. 4 is a partial cross section taken on line i-4 of FIG. 3;

FIG. 5 is a side view thereof; and

FIG. 6 is an enlarged perspective view of a corner of the bobbin.

In FIG. 1 the winding bobbin 1, which is made of suitable insulating plastic material, is shown having thereon a coil 2 in a number of precision wound layers. The preferred material for the bobbin is a glass polyester material, known by the tradename Glastic. The coil windings are of a normal transformer winding wire which has thereon an enamel insulating coating 3. The coil is wound on a central tube 4 and is constrained in a position between the ends thereof by end flanges 5 and 6 of the bobbin.

The most convenient configuration of transformer core 7 is one having a generally rectangular shape as shown in FIG. 3, since most conveniently the transformer core is made as a stacked group of grain-oriented lamina. Thus, the bobbin may advantageously have a rectangularly shaped interior cross section which closely approximates the shape of the transformer core to be utilized. In actual practice the spacing between the transformer core 7 (FIG. 3) and the tube 4 of the bobbin 1 need not be as great as shown on the drawing and, hence, the coil will be securely held on the transformer core.

The exterior surface of the tube 4 has round corners 8 (FIGS. 3 and 6). The round corners are required so that the bending radius around which the coil windings are turned is increased and therefore the insulation 3 on the wire does not crack. To control the spacing of the windings along the exterior surfaces of the tube 4, a series of spacing ribs 9, which are generally pyramidal in shape, are placed on each the four rounded corners 3 of the tube. A slot til is provided for bringing the interior end of the coil winding out from the interior of the coil, the slot 10 lying in a plane which is generally parallel with one of the exterior surfaces of the tube 4 (FIG. 3) and inclined away from the end of the tube through the flange (FIG. 4).

On flange 6 there is provided a terminal section 11 as an integral part thereof. The terminal section 11 includes a raised wall portion 12 having therein a series of slots 13. A strengthening and aligning rib 14 is formed on the side of wall 12 away from the coil 2. Into at least some of the slots 13 are inserted terminal connectors 15. While, as shown, only two of the slots 13 are so provided, the third slot may be equipped to provide a connection for a third tap for the transformer. Insulating walls 16a are formed between the slots 13 so as to lengthen the arc-over distance between the connectors 15.

The terminal connectors 15 are metallic members consisting of two sections 16 and 17 at right angles to each other. The first section 16 has therein a resilent hook portion 18 (FIG. 4) bent at an acute angle to the main body of the section and shoulders 19 (FIG. 1) which cooperate to secure the connectors to terminal section 11 through Wall 12. When the section 16 of the connector 15 is inserted in a slot 13 of the wall 12 the outwardly extending portion 14 hooks on the far side of the wall 12 and the shoulders 19 engage the near side of the wall to securely lock the connector 15 in the terminal wall. As shown, the outer end of the section 15 is provided with a hole 29 into which an external conductor may be inserted for connection of the coil in an electrical circuit. The other section 17 of terminal connector 15 is a gripper connector consisting of a generally U-shaped member 21 which may be clamped about an end of the coil Winding to make a secure connection; the interior surface of the legs thereof being provided with a series of sharp edged teeth 22 for making a good electrical connection with the amass? 3 conductor. While, as shown, the insulation has been stripped from the ends of the winding, it should be noted that the teeth 22 will normally bite through the insulation provided on the winding of a transformer coil.

The starting slot 1th is provided in the flange 6 adjacent to the terminal wall 12, the starting slot being parallel to one exterior wall portion of the central tube a of the bobbin (FIG. 3), the inner wall portion 23 of the slot being an integral extension of that exterior Wall portion of the tube 4. The outer end of the interior of the Winding may thus be led out through the slot and through a locking groove 24 (FIG. which is at right angles to the starting slot and parallel with the terminal wall 12. An insulating space is thus left by the starting end of the winding and the finish end of the coil which serves to reduce the voltage stress on the insulation (PEG. 1). A compartment 25 is provided beneath the terminal wall 12 on the exterior of the flange 6 into which the outer end of the winding may be led after completion of the coil by the addition of a lower wall 26 on the fiange 6. This compartment is connected to the central part of the bobbin by apertures 27 (FIG. 3).

An inclined plane, or Wedge, 28 is provided on the wall of the central tube adjacent to the starting slot 1% to lead the winding into a position away from the flange 6 after the winding has completed 270 degrees of its turn. Thus, it will be noted (FIG. 4) that at the end adjacent the starting groove the wedge 28 reached a dimension substantially that of the diameter of the wire and terminates at a point approximately two thirds of the distance across the wall of the central tube.

From the above, it will be noted that a coil may be easily wound on the bobbin by placing the end of the winding wire into the starting slot iii and twisting the wire at right angles into locking groove 24 to secure the end of the wire to the bobbin. On rotation of the bobbin (counterclockwise as viewed in FIG. 3) the wire Will fall into that space which is immediately adjacent to the side flange 6 of the bobbin and bounded by first rib 9. The wire will follow the same set of spaces in a straight line 270 degrees about the transformer bobbin. As it is wound along the fourth wall the wire engages the inclined plane 28 and is forced into the space immediately adjacent the initial turn of wire. Hence, the wire will be placed in the second space on the next succeeding turn. This winding will continue and the first layer of wire on the fourth Wall thus acts as a wedge to move next succeeding wind into the next succeeding space. Thus the winding when complete will be a truly precision wind in that all of the winding on the three sides will be directly parallel with the flanges and only the windings on the fourth wall will crossover, i.e., be at an angle with respect to the flanges. Thus, the build-up of the crossover is closely controlled. The ends of the coil may then be secured to terminal connectors 15 as shown in HG. 1, the outer end of the coil wire being led into and out of compartment 25 by apertures 27 so that the terminal lay of wire lies flat against the completed coil.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A coil winding bobbin adapted to closely surround a transformer core of rectangular cross-section comprising a tube of rectangular cross-section similar in shape to that of the transformer core and composed of electrical insulating material, said tube having flanges at opposite ends for constraining the coil winding within the extremities of the tube, said tube being formed on its outer surface only at the corners thereof with spaced grooves for receiving and positioning the turns of the coil winding, the bottoms of said grooves being rounded about the corners, whereby the bending radius of the winding at said corners is increased without reducing the minimum thickness of the tube walls.

2. A coil winding bobbin as defined in claim 1, wherein one of said flanges is formed with an integral terminal portion having opposite exterior faces and formed with a plurality of slots passing therethrough, and elongated terminal connectors inserted through said slots and having projecting portions engaging the opposite exterior faces of said terminal portion for securing the connectors thereto.

References Cited by the Examiner UNETED STATES PATENTS 1,668,302 5/28 Auty 336-229 X 1,760,975 6/30 Davis et a1. 336-192 X 1,763,114 6/30 Wermine 336-208 X 1,887,470 11/32 Twort 336-l92 2,633,629 4/53 Crookston 2421 17 X 2,795,765 6/57 Stroble 336l98 X 2,892,598 6/59 Dudley 2421l7 X 3,008,108 ll/61 Baker et a1. 336229 X 3,076,165 1/63 Weyrich 336192 X JOHN F. BURNS, Primary Examiner. 

1. A COIL WINDING BOBBIN ADAPTED TO CLOSELY SURROUND A TRANSFORMER CORE OF RECTANGULAR CROSS-SECTION COMPRISING A TUBE OF RECTANGULAR CROSS-SECTION SIMILAR IN SHAPE TO THAT OF THE TRANSFORMER CORE AND COMPOSED OF ELECTRICAL INSULATING MATERIAL, SAID TUBE HAVING FLANGES AT OPPOSITE ENDS FOR CONSTRAINING THE COIL WINDING WITHIN THE EXTREMITIES OF THE TUBE, SAID TUBE BEING FORMED ON ITS OUTER SURFACE ONLY AT THE CORNERS THEREOF WITH SPACED GROOVES FOR RECEIVING AND POSITIONING THE TURNS OF THE COIL WINDING, THE BOTTOMS OF SAID GROOVES BEING ROUNDED ABOUT THE CORNERS, WHEREBY THE BENDING RADIUS OF THE WINDING AT SAID CORNERS IS INCREASED WITHOUT REDUCING THE MINIMUM THICKNESS OF THE TUBE WALLS. 